1. Field of the Invention
This invention resides in axial force electrical machines that produce an axial force by shifting the air gap relationship between stator and rotor sections, wherein an axial thrust is produced by offsetting the rotor section in respect to the stator section. The greater the offset, the greater the axial force produced.
One of the major electrical machines having a large axial thrust is the vertical hollow shaft motor used for pumping water. These vertical hollow shaft motors used for pumping liquids in industry, municipalities and agriculture often have large axial loads that cause problems with ball bearings and other load bearing units of the motor. Some of these units contain stacked angular contact ball bearings in tandem mountings. Others require large spherical roller thrust bearings often requiring water to cool oil contained in said machine.
The present axial air gap machines utilize the magnetic force produced in the air gaps to compensate for axial loads.
2. Description of the Prior Art
Numerous attempts have been made in the past to increase the efficiency and reduce the energy consumption of electric machines. It should be noted however, that vertical hollow shaft motors produce an axial thrust that is detrimental to ball bearings and other load bearing units contained in said motors.
U.S. Pat. No. 3,296,475 to Park relates to dynamo-electric machines, rotors therefor. The patent describes an axial air gap machine having a lower rotor resistance thereby reducing power losses in said machine.
U.S. Pat. No. 3,304,450 to Bask, Jr., et al., describes an axial air gap dynamo-electric machine, wherein said machine is brushless and contains a rotor spaced apart from a stator armature by an axial air gap. A rotor disc, as described above, has at least one of its sides juxtaposed to a stator core provided with an armature winding with a narrow axial air gap between the faces of the stator and of the rotor.
U.S. Patent to Mori, et al., discloses a method for producing a magnetic core for an electric rotating machine which has an axially spaced air gap as in the case of a disc-type rotating machine.
U.S. Pat. No. 4,207,487 to Beyersdorf describes a disc-type, dynamo-electric machine having two stator and one rotor, active air gaps between each stator and the rotor, two annular energizing windings in the stators, and two non-active or auxiliary air gaps formed in a smooth region between the stators and the rotor.
U.S. Pat. No. 5,093,596 to Hammer relates to a combined linear-rotary direct drive step motor which provide both linear and rotary motion over a predefined range, e.g., along a portion of the longitudinal axis of the rotor shaft. The rotor and stator of the rotary step motor are described as having teeth.
U.S. Pat. No. 5,177,932 to Scott discloses a disc-type machine having a plurality of alternating stator and/or rotor sections. The stator has micro-laminated stator teeth molded from cut steel particles, mounted on a large disc of composite fiber material which is the main structure component of each stator section.
U.S. Pat. No. 5,777,421 to Woodward Jr. teaches a disc-type electrical machine having enhanced efficiency and effectiveness. The machine comprises a housing unit, a stator connected to said housing unit, a shaft rotatably connected to the stator housing unit with rotation means. A rotor connected to the shaft wherein the stator surface area and the rotor surface area are serrated.
As can be seen from the foregoing, there is an ongoing research effort to build better and more efficient electrical machines. The present axial force electrical machine solves the problem of undesired axial forces produced in vertical hollow shaft motors by offsetting the rotor section in respect to the rotor section of said motor.